1. Field of the Invention
This invention relates to systems for displaying surfaces of internal structures within solid bodies, and, more particularly, to systems for displaying surfaces of data acquired with a surface coil.
2. Description of Related Art
It is important to non-invasively visualize internal structures of a subject for various reasons. If the subject is a living person, it is necessary to view internal structures to make a diagnosis. One very important use is to visualize arteries and veins of the heart of a subject to determine if they are occluded. This is important in predicting cardiac arrest, and determining the health of the subject's heart. In the past, exploratory surgery, and catheter procedures have been used to determine narrowing, stenosis, and occlusion of vessels. These are very involved, painful and risky.
Multi-dimensional arrays of data representing one or more physical properties of a subject at regular grid positions within the interior of solid bodies have been acquired using magnetic resonance (MR) imaging systems. MR imaging employing external coil has been used to determine stenosis and occlusion. An external coil is typically one which encompasses the entire subject, or the entire portion of the subject being imaged. This imaging method produces planar, or slice, images of an imaging plane oriented through the heart. This is not nearly as invasive and much less risky than other procedures. A plane is selected which passes lengthwise through a coronary vessel. This produces a good image of the vessel which is in the imaging plane, however, many images of different imaging planes may be required to produce image the entire vessel. The images are discontinuous since they would be the composite of many different images taken at different imaging planes. It becomes difficult for the operator to mentally construct a three-dimensional shape and orientation of the vessel from the images. Also, there is no guarantee that no portion of the vessel has been omitted.
Three-dimensional MR image data sets have also been constructed using a external coil, however their large field of view and lack of detail do not allow accurate diagnosis of cardiac vessels. The data sets have been used to generate visual images of the interior structures within the subject. Surfaces of structures within the data set may then identified and shaded as described in U.S. Pat. No. 4,719,585, granted Jan. 12, 1988 by Cline et al.; segmented and color coded as described in U.S. Pat. No. 5,187,658 issued Feb. 16, 1993 "System And Method For Segmenting Internal Structures Contained Within The Interior Region Of A Solid Object" by Cline, Lorensen; then displayed to an operator. Both of the patents referenced here are assigned to the present assignee and hereby incorporated by reference. The visual images thus produced can be used for medical purposes such as diagnostics or for the planning of surgical procedures.
MR data sets have also been acquired employing a surface coil, instead of an external coil, to localize the MR image field of view to the heart to provide increased detail of cardiac vessels. A surface coil is typically a planar coil place on the surface of the subject at approximately the location where an image is desired. Surface coils receive MR response signals from a localized region of the subject, with its sensitivity dropping off away from the surface coil and to each side. Even though the surface coil provides better localization than external coils, the surface coil exhibit a different sensitivity profile which causes distortion, providing images which may not be used for cardiac vessel diagnosis.
Currently, there is need for a non-invasive method of providing detailed images of structures for diagnostic purposes.